Drop tank

In aviation, a drop tank (external tank, wing tank, or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in the event of emergency. In aviation, a drop tank (external tank, wing tank, or belly tank) is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in the event of emergency. The primary disadvantage with drop tanks is that they impose a drag penalty on the aircraft carrying them. External fuel tanks will also increase the moment of inertia, thereby reducing roll rates for air maneuvres. Some of the drop tank's fuel is used to overcome the added drag and weight of the tank itself. Drag in this sense varies with the square of the aircraft's speed. The use of drop tanks also reduces the number of external hardpoints available for weapons, reduces the weapon-carrying capacity, and increases the aircraft's radar signature.